H. Funaba

H. Nakanishi

I. Yamada

T. Hatae

T. Minami

Y. Itoh

National Institute for Fusion Science (NIFS-Repository)

Objective of development of new data process-ing system. An objective of the research projectis to develop a new digital data operation system forthe high repetition Nd:YAG Thomson scattering mea-surement. The creation of the dedicated system for theNd:YAG Thomson measurement considerably improvesthe data quality of the data of electron density and tem-perature measurement on the fusion plasma experiment.Our target is especially for the deuterium experiment ofthe LHD project. The development of an advanced dataacquisition system for the Nd:YAG Thomson scatteringmeasurement provides precise data of LHD plasma thatis required in the deuterium experiment.Procedure of research The project collaboratedwith Kyoto university, JAEA, and NIFS has startedtwo years ago. First we start with a conceptual de-sign for the data processing system. We investigate thenew high speed AD convertor construction that is opti-mized for the high speed scattered light signal detectionof the need:YAG Thomson measurement. In the activity,we found several problems of the system, then we havesearched for solutions. The achievements are reﬂected inthe conceptual design, and we ﬁnish the design. As anext step, in this ﬁscal year we designed the test moduleof the data processing system based on the conceptualdesign. We also perform a preliminary performance testof the system using evaluation boards of the components(AD convertor, FPGA, Diﬀerential ampliﬁer).Achievements of research We propose a high speedNd:YAG Thomson scattering analog to digital converter(HYADC). The HYADC can directly convert the highspeed signal of the Nd:YAG Thomson measurement in-stead of the conventional charge integral AD convertor.The HYADC has an advantage of an improving data ac-curacy compared with the conventional system to be ableto convert precisely a waveform of the scattered light tothe digitized data, because the amount of the informa-tion of the scattered light considerably increase by thehigh sampling rate conversion. The HYADC also has an-other advantage that is easy to reduce the backgroundlight from the measured scattered light signal. The re-duction is directly performed from the waveform analy-sis without other hardware which detect the backgroundsignal. The HYADC is also the appropriate and an indis-pensable data system for the multi path Thomson scat-tering measurement. The scattered light signals of multipulse are easily separated from the waveform data.The HYADC can convert the scattered light sig-nal by 12 bits accuracy and 500 MHz frequency usinghigh speed pipeline type AD convertor chips ( ADS5463Texas Instruments inc. ), then the HTADC fulﬁll theperformance requirement of the Nd:YAG Thomson scat-tering measurement with aﬀordable cost. A problem ofan increase of data volume that is caused by the highsampling rate and a large data storage system is re-quired for the long time plasma discharge is solved bythe method that is the data corresponding to the periodof the scattered light detected are extracted by the hard-ware system. The period of the scattered light detected(τ ∼ 200ns) is shorter than that of the plasma discharge.!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~SignalTrigerControlControl Unit500MHz 12bitAD ConverterClockAddressCounter1AddressCounter2Main FIFO Buffer MemoryRingBuffer memoryBuffer ampliﬁerBuffer ampliﬁerEther NetSiTCPFPGAEther NetSiTCPData ServerSiTCPFIFO Buffer MemoryADS5463Fig. 1: Schematic diagram of fundamental structure ofdigitizer module.Figure 1. shows the fundamental structure of thedesigned digitizer module. The digitizer has the ringbuﬀer memory to store the digitized data temporarilyfrom the start of the plasma discharge. When the ringbuﬀer memory is full, the address counter of the mem-ory goes back to the start address and the memory isoverwritten by the new sampling data. When the trig-ger signal that is synchronized with the laser injectionto the plasma input to the module, the data stored pro-cedure in the ring buﬀer memory is stopped, and thedigitized data of ∼ 2µsec before and after the laser in-jection are stored. The period that corresponds to thescattered light detected is calculated and the data trans-ferred to the main memory. After the end of the transfer,the module waits the next trigger of the laser injection.Conclusion and next plan We have ﬁnished the cir-cuit design of the digitizer module and the logic circuitdesign of the FPGA. We start the preliminary perfor-mance test for AD conversion and the data extract pro-cedure using the evaluation boards of the FPGA, ADconvertor, and the diﬀerential ampliﬁer. In the next ﬁs-cal year, we have a plan to carry out the board designand to produce the test module for the performance eval-uation.189§25. Development of New Data Processing System for High Repetition Nd:YAG Thomson Scattering MeasurementMinami, T. (Kyoto Univ.),  Nakanishi, H., Funaba, H., Yamada, I., Itoh, Y.,  Hatae, T. (JAEA)

Development of New Data Processing System for High Repetition Nd:YAG Thomson Scattering Measurement

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Development of New Data Processing System for High Repetition Nd:YAG Thomson Scattering Measurement

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